One of the five most common problems seen in birth defect clinics today is Prader-Willi Syndrome. Among the characteristics of this syndrome are mental deficiency, short stature, marked obesity and sexual infantilism. Prader-Willi Syndrome often starts to become manifest during the first year of life but is difficult to diagnose because, except for an overwhelming hyperphagia which becomes the dominant symptom with time, the symptoms of the disease are very indeterminate. As a result, the initiation of remedial training (to overcome the mental retardation) and a drastic weight control program (required to combat the massive, compulsive and life-threatening overeating) is frequently delayed beyond the time that they should be initiated.
Prader-Willi Syndrome is a complex syndrome of unknown origin. The genetic role in the disease has been difficult to study since individuals suffering with the syndrome do not reproduce and frequently die during their early twenties. Nevertheless, it appears clear that the condition is not sex linked and has a low recurrence rate of not greater than 1%. It has been observed that approximately 50% of Prader-Willi cases exhibit a defect in the 15q region of chromosome 15 but this defect is also present in a few individuals without Praeder-Willi Syndrome. There are no specific biochemical tests which exist at the present in order to diagnose the syndrome. That fact, coupled with the indeterminate symptoms, frequently delays diagnosis. Further, once diagnosed, only palliative treatment of the symptoms is available to the physician.
The present invention is based on a discovery which resulted from an examination of the steroid sulfate profile of children suffering with Prader-Willi Syndrome and which demonstrated the presence of two characteristic metabolic patterns. In one group, dehydroepiandrosterone sulfate was the only sulfo-conjugate peak detected and, in the second, the DHEA-sulfate was accompanied by four other more polar sulfo-conjugate peaks. Based on this evidence, it was recognized that one of three etiologies could be involved, namely, 1.) low DHEA sulfate levels in the plasma due to a defect in one of the early steps in the biosynthetic pathway, 2.) excessive amounts of DHEA-sulfate metabolites associated with either a receptor or post-receptor defect, and 3.) excessive amounts of some DHEA-sulfate metabolites caused by a metabolic block in the pathway and consequent accumulation of other products. Further conformation of the existence of a steroidogenic defect comes from our recent observations that plasma etiocholanolone levels are low in patients with Praeder-Willi Syndrome. Thus, these data are consistent with a defect in the pathway leading to etiocholanolone synthesis. lone and certain of related compounds to eliminate this deficiency in individuals suffering with the syndrome. The consequence of relieving the deficiency is also advantageous in effecting weight loss or at least decreasing the rate of weight gain.
The steroid dehydroepiandrosterone (3-beta-hydroxyandrost-5-en-17-one, DHEA) and its sulfate derivatives are major steroid adrenal secretory products in humans. DHEA is metabolized to testosterone (17-beta-hydroxy-androst-4-en-3-one) and estradiol (estra-1, 3, 5 (10)-triene-3, 17-diol), two major sex hormones in humans. Other metabolites of DHEA include alpha-etiocholanolone (5-beta-androstan-3-alpha-ol-17-one, hereinafter referred to as alpha-ET) and beta-etiocholanolone (5-beta-androstan-3-beta-ol-17-one, hereinafter referred to as beta-ET) and were, until recently, considered to be inert metabolic end products which were merely conjugated as glucuronides or sulfates and excreted in the urine. Alpha-ET is a major metabolite of DHEA, and in normal individuals, is excreted in the urine in amounts of about 3-5 mg per day, whereas beta-ET is a minor metabolite in man.
Yen, et al. (Lipids 12:409, 1977) disclosed that DHEA, administered by a variety of routes, decreased the rate of weight gain in a strain of genetically obese mice. Coleman, et al. (Diabetes 31:830, 1982) demonstrated that DHEA treatment had a marked preventive effect on the development of diabetes in either genetically obese or diabetic mice. Furthermore, they indicated that for the maximal beneficial effect, DHEA had to be ingested. Coleman, et al. (Endocrinology 115:239-243, 1984) disclosed that alpha-ET and beta-ET, but not androsterone or epiandrosterone, were four time more effective than DHEA in preventing the development of diabetes in C57BL/KsJ-db/db diabetic mice. Alpha-ET and beta-ET reduced blood sugar, increased plasma insulin concentrations and provided a protective effect on the pancreas, as shown by an increase in the number of granules in the islet betacells. These results demonstrated that both compounds had physiological significance and were not merely end products of sterol metabolism.
Coleman, et al. (U.S. Pat. No. 4,518,595, incorporated by reference) disclosed that oral administration of DHEA restored hyperglycemia to normal levels and improved glucose tolerance even in severely diabetic mammals. Coleman, et al. (U.S. Pat. No. 4,507,289, incorporated by reference) taught the use of alpha- and/or beta-ET and an estrogen for the treatment of diabetes, obesity syndromes and associated hypercorticoidism. The activity of alpha-ET and beta-ET suggests that DHEA may actually be exerting its effects through its metabolites. The advantage of both alpha-ET and beta-ET over DHEA is that they cannot be converted to estradiol or testoserone.
Coleman (Endocrinology 117:2279-2283, 1985) disclosed that alpha-ET and beta-ET, when supplied in the diet, have anti-obesity properties. They were effective both in preventing and in arresting the development of obesity as well as in facilitating weight reduction after obesity and this has been established in diabetic, genetically obese mice. Finally, in U.S. Pat. No. 4,666,898 (incorporated herein by reference) Coleman and Applezweig disclose the use of etiocholanolones for the treatment of obesity, diabetes and other symptoms of hypercorticoidism.
It was discovered that alpha-ET and beta-ET administered orally, parenterally i.p., i.m. or i.v. are both rapidly oxidized at the C-3 position to form etiocholanedione (5-beta-androstanedione, hereinafter referred to as ET-dione) and that ET-dione can serve as a superior source of circulating blood levels of free (nonconjugated) alpha-ET. Once formed, the ET-dione is reduced only to alpha-ET, which may then be conjugated and excreted. This dynamic interconversion of alpha-ET and ET-dione provides the means of achieving alpha-ET blood levels through the use of ET-dione serving as a pro-drug for alpha-ET. In addition, whereas conjugation and excretion rapidly removes alpha-ET from the blood stream, ET-dione must be reduced to alpha-ET before being eliminated from the body, and may therefore have a longer circulatory half-life than alpha-ET. Animal and human pharmacokinetic data demonstrate that ET-dione produces increased blood levels of free alpha-ET. This increased blood level may be due to improved absorption of ET-dione over alpha-ET. This is the subject of U.S. application Ser. No. 078,610, filed July 28, 1987 and incorporated herein by reference.
The evidence referred to above and described in more detail below provides the missing suggestion. The accumulation of unidentified steroid sulfates in some serum from Prader-Willi Syndrome children is an indicator that there is a blocked biosynthetic pathway. No enzyme deficiency state has previously been associated with this syndrome. Adrenal steroid levels had previously been reported as normal and this is the first discovery of a decreased serum level for known steroids. Our evidence indicates individuals with Prader-Willi Syndrome have an enzyme deficiency syndrome of unknown parameters which causes a defect in a steroid biosynthetic pathway which apparently leads to a block in etiocholanolone synthesis, which in turn contributes to obesity.